Graphene wiring structure and semiconductor device using the same

ABSTRACT

A graphene wiring structure of an embodiment has: an amorphous or polycrystalline insulating film; and a multilayer graphene on the insulating film. The multilayer graphene including a plurality of graphene crystals having a zigzag direction is oriented at 17 degrees or less with respect to an electric conduction direction on the insulating film.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority fromJapanese Patent Application No. 2017-056529, filed on Mar. 22, 2017; theentire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate to a graphene wiring structure, asemiconductor device, a method for manufacturing a graphene wiringstructure, and a method for manufacturing a wiring structure.

BACKGROUND

A graphene is a two-dimensional nanomaterial formed of carbon atoms. Anedge of the two-dimensional material is a topological peculiar part, andphysical properties thereof change according to a structure thereof. Agraphene has two types of edge structure called zigzag (ZZ) and armchair(AC). It has been theoretically and experimentally reported that due tothese differences, a change in physical properties such as electricalcharacteristics (generation of a band gap in an ultrafine grapheneformed of AC edges) or magnetic properties (transition betweenantiferromagnetism and ferromagnetism in an ultrafine graphene formed ofZZ edges) occurs.

In order to apply such physical properties to an actual device, agraphene processing technique to control an edge structure at an atomiclevel is necessary, and it is required to realize this technique on alarge area substrate of 300 mm or the like for industrial applications.A large area graphene growth technique already exists. However, a metalthin film serving as a substrate is polycrystalline, and therefore agrowing graphene also becomes polycrystalline inevitably. This makesprocessing in a specific direction difficult. Therefore, like othermaterials, a graphene essentially needs a single crystal/large areagrowth technique for device application. The inventors have found asingle crystal/large area graphene growth method.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a graphene wiring structure accordingto an embodiment;

FIG. 2 is a graph illustrating a relationship between an angle of azigzag direction of graphene crystals with respect to an electricconduction direction according to an embodiment and a band gap;

FIGS. 3A, 3B, 3C, 3D are schematic diagram of a planar graphene sheetaccording to an embodiment;

FIG. 4 is a process diagram of a graphene wiring structure according anembodiment;

FIG. 5 is a process diagram of a graphene wiring structure according toan embodiment;

FIG. 6 is a process diagram of a graphene wiring structure according toan embodiment;

FIG. 7 is a schematic diagram of a graphene wiring structure accordingto an embodiment;

FIG. 8 is a process diagram of a graphene wiring structure according toan embodiment;

FIG. 9 is a process diagram of a graphene wiring structure according toan embodiment;

FIGS. 10A, 10B, 10C, 10D are process diagrams of a graphene wiringstructure according to an embodiment;

FIGS. 11A and 11B are process diagrams of a graphene wiring structureaccording to an embodiment;

FIG. 12 is a schematic diagram of a wiring structure according to anembodiment;

FIG. 13 is a process diagram of a wiring structure of an embodiment;

FIG. 14 is a process diagram of a wiring structure of an embodiment;

FIG. 15 is a process diagram of a wiring structure of an embodiment;

FIG. 16 is a process diagram of a wiring structure of an embodiment;

FIG. 17 is a process diagram of a wiring structure of an embodiment;

FIG. 18 is a process diagram of a wiring structure of an embodiment;

FIG. 19 is a process diagram of a wiring structure of an embodiment;

FIG. 20 is a schematic diagram of a graphene wiring structure accordingto an embodiment; and

FIG. 21 is a schematic diagram of a semiconductor device according to anembodiment.

DETAILED DESCRIPTION

A graphene wiring structure of an embodiment has: an amorphous orpolycrystalline insulating film; and a multilayer graphene on theinsulating film. The multilayer graphene including a plurality ofgraphene crystals having a zigzag direction is oriented at 17 degrees orless with respect to an electric conduction direction on the insulatingfilm.

First Embodiment

Hereinafter, embodiments of the present disclosure will be describedwith reference to the drawings. Components with the same referencenumerals indicate similar components. Note that the drawings areschematic or conceptual, and a relationship between a thickness and awidth of each portion, a ratio coefficient of a size between portions,and the like are not necessarily the same as actual ones. Even in a caseof illustrating the same portion, the drawings may illustrate the sameportion such that dimensions and ratio coefficients are different fromone another. Arrows in the drawings indicate an orientation direction ofa crystal, a polarization direction, and the like.

A graphene wiring structure according to a first embodiment includes anamorphous or polycrystalline insulating film, and a multilayer grapheneincluding a plurality of graphene crystals having a zigzag directionoriented at 17 degrees or less with respect to an electric conductiondirection on the insulating film.

FIG. 1 illustrates a schematic cross-sectional diagram of the graphenewiring structure according to the first embodiment.

A graphene wiring structure 10 of FIG. 1 includes a multilayer graphene2 on an insulating film 1. The electric conduction direction which is alongitudinal direction of the multilayer graphene 2 is defined as an Xdirection, and a wiring height direction which is a lamination directionof graphene sheets constituting the multilayer graphene 2 is defined asa Y direction. A Z direction is not illustrated in FIG. 1, but is adirection perpendicular to an X-Y plane. A wiring width direction whichis a short direction of the multilayer graphene 2 is defined as a Zdirection.

The insulating film 1 is an insulating film supporting the multilayergraphene 2. The multilayer graphene 2 is present on the insulating film1. The multilayer graphene 2 is preferably present right above theinsulating film 1. In addition, the multilayer graphene 2 is preferablyin direct contact with the insulating film 1. The insulating film 1 isnot a single crystal film, but an amorphous or polycrystalline film.

The insulating film 1 is not particularly limited as long as beinginsulating, but is preferably a film containing at least one selectedfrom the group consisting of SiO₂, Al₂O₃, TiO₂, and the like.Furthermore, the insulating film 1 is more preferably any one selectedfrom the group consisting of a SiO₂ film, an Al₂O₃ film, a TiO₂ film,and the like. The thickness of the insulating film 1 is, for example,0.01 μm or more and 1000 μm or less.

X-ray diffraction analysis confirms whether the insulating film 1 is anamorphous or polycrystalline film. If a peak derived from a crystalperiod does not appear in an X-ray diffraction spectrum, the insulatingfilm 1 is amorphous. If a peak derived from a crystal period appears inan X-ray diffraction spectrum, the insulating film 1 is polycrystalline.

The multilayer graphene 2 includes a plurality of graphene crystalshaving a zigzag direction oriented at 17 degrees or less with respect toan electric conduction direction. The multilayer graphene 2 has astructure having a plurality of planar graphene sheets laminated. Theplanar graphene sheets include a plurality of graphene crystals having azigzag direction oriented at 17 degrees or less with respect to anelectric conduction direction. Each of the planar graphene sheets may bea single atomic layer formed of carbon atoms or a single atomic layer inwhich a part of carbon atoms is bonded to an oxygen atom, a nitrogenatom, or the like.

The lamination number of planar graphene sheets is not particularlylimited, but is preferably 10 or more and 100 or less, for example. Adistance of the multilayer graphene 2 in a lamination direction is aheight of the multilayer graphene 2. A height H of the multilayergraphene 2 is, for example, 3 nm or more and 35 nm or less. In a casewhere an interlayer substance is present between layers of themultilayer graphene 2, an interlayer distance of the multilayer graphene2 is increased from 0.335 nm to, for example, 0.5 nm or more and 1 nm orless. Therefore, in a case where an interlayer substance is containedbetween the layers, the height H of the multilayer graphene 2, is 5 nmor more and 100 nm or less. The interlayer substance is preferably asubstance to contribute to lowering resistance of the multilayergraphene 2, and for example, is a metal halide such as iron chloride ormolybdenum chloride, or a halogen without being particularly limited.

A width W of the multilayer graphene 2 is a short side in a directionparallel to a plane of the insulating film 1 of the multilayer graphene2. The width W of the multilayer graphene 2 is preferably 3 nm or moreand 10 nm or less.

A length L of the multilayer graphene 2 is a long side in a directionparallel to a plane of the insulating film 1 of the multilayer graphene2. The length L of the multilayer graphene 2 is not limited, but is 10μm or more.

A ratio (W/H) between the height H and the width W of the multilayergraphene 2 is preferably 0.1 or more and 10 or less. A too small valueof the ratio makes electric resistance high, and is not preferable. Atoo large value of the ratio causes mechanical destruction easily, andis not preferable.

A graphene has two types of edges of a zigzag edge and an armchair edge.When there is a zigzag edge in a length direction of wiring, that is,when an electric conduction direction is a zigzag direction, theresistance is low. However, when there is an armchair edge in the lengthdirection of the wiring, that is, when the electric conduction directionis the armchair direction, a graphene becomes semiconductive. When thezigzag direction faces the electric conduction direction, the wiring ispreferable because of its low resistance. In the embodiment, the lengthdirection of the multilayer graphene 2, which is the longitudinaldirection of the multilayer graphene 2 is defined as an electricconduction direction of the graphene wiring structure 10.

Crystallinity of a graphene is influenced by crystallinity of asupporting base material thereof. Therefore, if the supporting basematerial is formed of single crystals, the crystal orientation of thegraphene easily becomes uniform. However, wiring using a graphene isexpected to be used for a semiconductor device, and it is not easy toform a single crystal film having a wafer size of 12 inches or the like.When a monocrystalline insulating film is formed in consideration ofwiring resistance of a graphene, very large cost is required, andfurthermore, the yield is low. Meanwhile, when a graphene is provided onthe amorphous or polycrystalline insulating film 1, the crystallineorientation of the graphene becomes random due to an influence ofcrystallinity of the insulating film. Therefore, resistance of thegraphene increases as it is. However, in the embodiment, it is possibleto control the crystal orientation of a graphene provided on theamorphous or polycrystalline insulating film 1. This makes it possibleto stably manufacture low resistance wiring with a polycrystallinegraphene.

The graph in FIG. 2 illustrates a relationship between an angle of azigzag direction of graphene crystals having a width of about 1 nm withrespect to an electric conduction direction and a band gap. As a roughtrend, the band gap of a graphene is inversely proportional to the widthof graphene crystals. Even if a graphene is semiconductive, that is,even if the graphene has a band gap, when the band gap can be exceededby heat of about room temperature, the graphene can be used as lowresistance wiring. When the zigzag direction deviates from the electricconduction direction, the band gap increases. However, a somewhat smallband gap can be exceeded by thermal energy. Therefore, even if thezigzag direction does not coincide with the electric conductiondirection, the multilayer graphene 2 becomes a low-resistance conductivematerial. As a result of first principle calculation, it has beenindicated that at a normal temperature, the resistance is low when anangle of the zigzag direction of a graphene with respect to the electricconduction direction is 17 degrees or less. Therefore, in theembodiment, the multilayer graphene 2 preferably includes a plurality ofgraphene crystals having a zigzag direction oriented at 17 degrees orless with respect to an electric conduction direction. The multilayergraphene 2 is more preferably formed of a plurality of graphene crystalshaving the zigzag direction oriented at 17 degrees or less with respectto the electric conduction direction. Hereinafter, when the angle of thezigzag direction of graphene crystals with respect to the electricconduction direction is 17 degrees or less, it is assumed that “thecrystal orientation of graphene crystals is uniform”. Incidentally, whenincluding a bent wiring structure, the graphene wiring structure 10includes many regions where the angle of the zigzag direction ofgraphene crystals largely deviates from the range of 17 degrees or less,and the resistance of the wiring is increased. Therefore, the graphenewiring structure 10 according to the first embodiment is preferablyapplied to a linear portion of the wiring, and preferably includes nobending. That is, the multilayer graphene 2 is preferably a laminate ofplanar graphene sheets, and more preferably a laminate of a plurality ofstrip-shaped graphene sheets having no bent portion such as curvedgeometry.

If it is possible to realize low resistance wiring only when the angleof the zigzag direction of graphene crystals with respect to theelectric conduction direction is within a very narrow range, it is noteasy to manufacture low resistance graphene wiring by making the crystalorientation uniform. However, in the embodiment, when the angle of thezigzag direction of graphene crystals with respect to the electricconduction direction is 17 degrees or less, the graphene crystals haveparticularly low resistance, and therefore it is possible to realize lowresistance wiring even with polycrystalline graphene. The smaller theangle of the zigzag direction of graphene crystals with respect to theelectric conduction direction is, the lower the resistance of the wiringbecomes. Therefore, the angle of the zigzag direction of graphenecrystals with respect to the electric conduction direction is morepreferably 13 degrees or less, and still more preferably 11 degrees orless. In polycrystalline graphene, it is difficult to make the angle ofthe zigzag direction of graphene crystals with respect to the electricconduction direction perfectly uniform, and therefore the angle of thezigzag direction of graphene crystals with respect to the electricconduction direction is only required to be 1 degree or more. The angleof the zigzag direction of graphene crystals with respect to theelectric conduction direction is preferably 0 degrees or more and 17degrees or less, more preferably 1 degree or more and 17 degrees orless, still more preferably 1 degree or more and 13 degrees or less, andfurther still more preferably 1 degree or more and 11 degrees or less.

In a case of a polycrystalline graphene, the graphene inevitablycontains a grain boundary. If there is a grain boundary, a cyclicstructure such as a five-membered ring or a seven-membered ring ispresent in addition to a six-membered ring in a plurality of graphenecrystals of the multilayer graphene 2. The angle of the zigzag directionof a graphene with respect to the electric conduction direction does notinclude this grain boundary.

The zigzag direction of a graphene with respect to the electricconduction direction can be measured by electron backscatter diffraction(EBSD) or with a scanning tunneling microscope (STM). Scanning isperformed from the center in a width direction of a planar graphenesheet on the outermost surface of the multilayer graphene 2 along theelectric conduction direction which is a wiring length direction. Aregion to be scanned includes the center of ten divided regions obtainedby dividing the multilayer graphene 2 into ten parts in the wiringlength direction. A region where 10 or more 6-membered ring structuresare continuously and regularly confirmed is defined as a graphenecrystal other than a grain boundary. The zigzag direction of graphenecrystals with respect to the electric conduction direction is determinedby measuring an orientation of a 6-membered ring structure in the regionwhere 10 or more 6-membered ring structures are continuously andregularly confirmed.

FIGS. 3A, 3B, 3C, and 3D each illustrate a schematic diagram of a planargraphene sheet containing a plurality of graphene crystals having thezigzag direction oriented at 17 degrees or less with respect to theelectric conduction direction.

FIG. 3A is a schematic diagram of a planar graphene sheet formed ofgraphene crystals having the zigzag direction oriented at 0 degrees withrespect to the electric conduction direction. The multilayer graphene 2is, for example, a laminate of the planar graphene sheets of FIG. 3A.The electric conduction direction is a direction of a line segmentconnecting center points at both ends of the planar graphene sheet inthe wiring length direction. More specifically, the width of one end ofthe planar graphene sheet in the wiring length direction is referred toas W₁, and the width of the other end thereof is referred to as W₂. Aline segment connecting a point of ½W₁ at one end and a point of ½W₂ atthe other end indicates the electric conduction direction. The graphenesheet illustrated in FIG. 3A has no grain boundary and is formed ofsingle crystals. The graphene sheet is formed of single crystals and thezigzag direction and the electric conduction direction are the same aseach other, and therefore low resistance wiring is obtained.Incidentally, both ends of the planar graphene sheet in the wiringlength direction are armchair edges, and the direction of the armchairedges is perpendicular to the electric conduction direction.

FIG. 3B is a schematic diagram of a planar graphene sheet includinggraphene crystals having the zigzag direction oriented at 3 degrees withrespect to the electric conduction direction and graphene crystalshaving the zigzag direction oriented at 7 degrees with respect to theelectric conduction direction. The multilayer graphene 2 is, forexample, a laminate of planar graphene sheets of FIG. 3B. The electricconduction direction and the like are similar to those in FIG. 3A. Inthe graphene sheet illustrated in FIG. 3B, a majority of graphenecrystals has the zigzag direction oriented at 17 degrees or less withrespect to the electric conduction direction. Such a planar graphenesheet includes a grain boundary because the graphene sheet includesgraphene crystals having different crystal orientations and the graphenecrystals are connected to each other. The grain boundary includesdefects, a 5-membered ring structure, a 7-membered ring structure, andthe like in addition to a 6-membered ring structure. Even such apolycrystalline graphene sheet has a crystal orientation, and thereforethe zigzag direction thereof is close to the electric conductiondirection. Therefore, the band gap of the graphene sheet is small, andthe multilayer graphene 2 obtained by laminating the graphene sheet isalso low resistance wiring. Graphene crystals oriented in the zigzagdirection at 7 degrees with respect to the electric conduction directionhave an inclination of 10 degrees with respect to graphene crystalsoriented in the zigzag direction at 3 degrees with respect to theelectric conduction direction. However, each of these inclinations hasthe zigzag direction oriented at 17 degrees or less with respect to theelectric conduction direction, and therefore a low resistance wiringmaterial is obtained. The multilayer graphene 2 obtained by laminatingmonocrystalline graphene sheets as illustrated in FIG. 3A is ideal.However, it is not easy to completely control the crystal orientationwith a wiring length of 100 μm or more, for example. When a completecrystal orientation is obtained, the yield is low, and such a case isnot practical. However, even if the crystal orientation cannot becontrolled completely, when the crystal orientation can be controlled toa certain extent, the multilayer graphene 2 is suitable as lowresistance wiring. The multilayer graphene 2 according to the firstembodiment has an advantage in that the multilayer graphene 2 isrelatively low resistance wiring within a range in which control of thecrystal orientation is easy. The multilayer graphene 2 which cannotcompletely control the crystal orientation but is low resistance wiringincludes graphene crystals having the zigzag direction oriented at 1degree or more and 17 degrees or less with respect to the electricconduction direction.

FIG. 3C is a schematic diagram of a planar graphene sheet includinggraphene crystals having the zigzag direction oriented at 0 degrees withrespect to the electric conduction direction, graphene crystals havingthe zigzag direction oriented at 17 degrees with respect to the electricconduction direction, and graphene crystals having the zigzag directionoriented at 0 degrees with respect to the electric conduction direction.The multilayer graphene 2 is, for example, a laminate of planar graphenesheets of FIG. 3C. The electric conduction direction and the like aresimilar to those in FIG. 3A. In the graphene sheet illustrated in FIG.3C, a majority of graphene crystals has the zigzag direction oriented at17 degrees or less with respect to the electric conduction direction.Like the graphene sheet of FIG. 3B, the grain boundary includes defects,a 5-membered ring, and the like. Graphene crystals having the zigzagdirection oriented at 17 degrees with respect to the electric conductiondirection are included, but the angle is 17 degrees or less. Therefore,the multilayer graphene 2 obtained by laminating planar graphene sheetsof FIG. 3C has also low resistance similarly to that of FIG. 3B.

FIG. 3D is a schematic diagram of a planar graphene sheet includinggraphene crystals having the zigzag direction oriented at 0 degrees withrespect to the electric conduction direction and graphene crystalshaving the zigzag direction oriented at 10 degrees with respect to theelectric conduction direction. The electric conduction direction and thelike are similar to those of FIG. 3A. In the planar graphene sheets ofFIG. 3B and FIG. 3C, grain boundaries are present along a directionnearly perpendicular to the electric conduction direction. Meanwhile,the grain boundary of the planar graphene sheet of FIG. 3D extends inthe wiring length direction, and faces a direction close to the electricconduction direction. Even in the structure having such a grainboundary, a majority of graphene crystals has the zigzag directionoriented at 17 degrees or less with respect to the electric conductiondirection. Therefore, the multilayer graphene 2 obtained by laminatingplanar graphene sheets of FIG. 3D is also preferable because of its lowresistance. In each of the planar graphene sheets illustrated in FIGS.3A to 3D, the zigzag direction of graphene crystals is oriented at 17degrees or less with respect to the electric conduction direction exceptfor the grain boundary.

Next, a method for manufacturing the graphene wiring structure 10according to the first embodiment will be described with reference tothe drawings. Process diagrams of the graphene wiring structure 10illustrated in FIGS. 4 to 6 are process diagrams for manufacturing thegraphene wiring structure 10 illustrated in the schematic diagram ofFIG. 7. FIGS. 4 to 7 are perspective diagrams. In the process diagram ofFIG. 4, a member provided with microcrystalline graphene 3 on theinsulating film 1 is illustrated. The microcrystalline graphene 3 is asmall graphene crystal of, for example, about 10 nm to 10000 nm. FIG. 4illustrates the zigzag direction of the microcrystalline graphene 3. Theinsulating film 1 is not formed of single crystals but ispolycrystalline. Therefore, when the microcrystalline graphene 3 isprovided on the insulating film 1, the crystal orientation is random dueto an influence of crystallinity of the insulating film 1. When thegraphene is grown as it is from this microcrystalline graphene 3, thegraphene extends depending on its crystallinity, and therefore apolycrystalline graphene having a random crystal orientation is formed.In the embodiment, a treatment for making the orientation of themicrocrystalline graphene 3 uniform is performed. Examples of themicrocrystalline graphene 3 include a single crystal graphene (singlelayer or multilayer) such as a single layer graphene grown from a singlecrystal catalyst, a multilayer graphene grown from a single crystalcatalyst, or a multilayer graphene obtained by organic synthesis. Themicrocrystalline graphene 3 has a small area, and therefore themicrocrystalline graphene 3 formed of single crystals can be easilymanufactured.

Examples of a treatment for making the orientation of themicrocrystalline graphene 3 uniform include, first, a method using aliquid crystal. A liquid crystal is applied onto the insulating film 1provided with the microcrystalline graphene 3 having a random crystalorientation, and a photo-orientation film is provided on the appliedliquid crystal and is irradiated with light. The orientation of theliquid crystal thereby becomes uniform. At this time, themicrocrystalline graphene 3 is influenced by change in orientation ofthe liquid crystal, and the orientation of the microcrystalline graphene3 becomes uniform like the liquid crystal. Then, it is only required toremove the photo-orientation film and the liquid crystal. It ispreferable to use at least one compound selected from the groupconsisting of an azobenzene derivative, a stilbene derivative, acyanobiphenyl, an azoxybenzene derivative, a carbonate derivative, and afluorine-containing biphenyl. These compounds each have a 6-memberedring structure containing carbon atoms like a graphene, and thereforehave an influence on the crystal orientation of the microcrystallinegraphene 3. The liquid crystal is preferably a compound having amolecular skeleton similar to a graphene of a six-membered ringstructure or the like.

Other examples of a treatment for making the orientation of themicrocrystalline graphene 3 uniform include a method using polarity ofthe insulating film 1 and a liquid crystal. A compound in which aplurality of hydrophilic groups and hydrophobic groups are alternatelyaligned is used for the insulating film 1. A liquid crystal having ahydrophilic group at one end and a hydrophobic group at the other end,and the microcrystalline graphene 3 are mixed, and the resulting mixtureis applied onto the insulating film 1. As a result, the hydrophilicgroups of the liquid crystal are aligned on a hydrophilic side of theinsulating film 1, and the hydrophobic groups of the liquid crystal arealigned on a hydrophobic side of the insulating film 1. The liquidcrystal is arranged on the insulating film 1 such that the orientationof the microcrystalline graphene 3 is also uniform due to theorientation of the liquid crystal. Then, it is only required to removethe liquid crystal.

Through any of the above treatments, a member in which themicrocrystalline graphene 3 having a uniform crystal orientation isprovided on the polycrystalline insulating film 1 illustrated in FIG. 5is manufactured. In FIG. 4, the directions of the arrows are notuniform, but in FIG. 5, the directions of the arrows are uniform. Withthis method, the orientation of crystals can be controlled, andtherefore it is possible to make the electric conduction direction in acase of processing into a wiring shape and the zigzag direction of agraphene uniform. A member provided with the microcrystalline graphene 3having a uniform crystal orientation on the polycrystalline insulatingfilm 1 is also manufactured by transferring the microcrystallinegraphene 3 having a uniform crystal orientation onto the insulating film1.

Examples of a method for transferring the microcrystalline graphene 3having a uniform crystal orientation onto the insulating film 1 includea method for providing the microcrystalline graphene 3 on a film havingan oriented side chain such as a photo-orientation film, andtransferring the microcrystalline graphene 3 onto the insulating film 1.The microcrystalline graphene 3 is bonded to an oriented side chain of aphoto-orientation film or the like, and light irradiation is performedto make the orientation of the oriented side chains to which themicrocrystalline graphene 3 is bonded uniform. Like a graphene, thisoriented side chain also has a molecular skeleton similar to a grapheneof a 6-membered ring structure containing a carbon atom or the like. Theorientation of the microcrystalline graphene 3 can be thereby madeuniform. By transferring the microcrystalline graphene 3 having auniform orientation onto the insulating film 1, the microcrystallinegraphene 3 having a uniform crystal orientation as illustrated in theprocess diagram of FIG. 5 is formed on the insulating film 1.

Other examples of a method for transferring the microcrystallinegraphene 3 having a uniform crystal orientation onto the insulating film1 include a method for transferring the microcrystalline graphene 3 byprocessing a monocrystalline graphene having a known crystal orientationinto a mold or the like.

Other examples of the method for transferring the microcrystallinegraphene 3 having a uniform crystal orientation onto the insulating film1 include a method using a graphene nanoribbon having a uniform crystalorientation in place of the microcrystalline graphene 3. A plurality ofgraphene nanoribbons having a uniform crystal orientation and a polymerare mixed. As a result, the graphene nanoribbons having a uniformorientation are in contact with the polymer. At this time, the polymerhas bent portions randomly, and therefore the crystal orientation in asingle graphene nanoribbon is uniform. However, the plurality ofgraphene nanoribbons each having a uniform orientation faces a randomdirection. Here, when the polymer is stretched, the plurality ofgraphene nanoribbons each having a uniform crystal orientation faces thesame direction (within ±10 degrees) while being in contact with thestretched polymer. By transferring the plurality of graphene nanoribbonseach having a uniform crystal orientation and facing the same direction(within ±10 degrees) to the insulating film 1, the plurality of graphenenanoribbons each having a uniform crystal orientation and facing thesame direction (within ±10 degrees) as illustrated in the processdiagram of FIG. 5 (microcrystalline graphene 3) is formed on theinsulating film 1.

In the member provided with the microcrystalline graphene 3 having auniform crystal orientation on the polycrystalline insulating film 1,illustrated in the process diagram of FIG. 5, when a graphene isadditionally grown with the microcrystalline graphene 3 as a nucleus, asillustrated in the process diagram of FIG. 6, a member in which thepolycrystalline graphene film 4 having a uniform crystal orientation(within ±17 degrees with respect to an electric conduction directionobtained later) is provided on the insulating film 1 is obtained. InFIG. 6, grain boundaries are indicated by a broken line. The averageparticle diameter of a graphene crystal of the polycrystalline graphenefilm 4 obtained here is larger than the width of the multilayer graphene2. This means that the polycrystalline graphene film 4 to become wiringlater can be obtained from crystal nuclei having a uniform crystalorientation. The average particle diameter of the graphene crystals ispreferably at least five times the width of the multilayer graphene 2.Incidentally, for additional growth of a graphene, a graphene filmformation process can be employed. For example, an ethylene gas or anacetylene gas is supplied as a raw material, and plasma chemical vapordeposition (CVD) is performed.

The member in which the polycrystalline graphene film 4 illustrated inthe process diagram of FIG. 6 is provided on the insulating film 1 ispatterned into a wiring shape to obtain the graphene wiring structure 10illustrated in the schematic diagram of FIG. 7. In the schematic diagramof FIG. 7, a plurality of the multilayer graphenes 2 of the graphenewiring structure 10 is present, and is arranged in parallel. A part ofthe grain boundaries of the polycrystalline graphene film 4 remains evenafter the member is patterned into a wiring shape, and the crystalorientation of a graphene crystal is uniform. Therefore, low resistancewiring is obtained. Incidentally, by repeating the steps illustrated inFIGS. 4 to 6, it is possible to increase the lamination number of themultilayer graphene 2.

A method for manufacturing the above graphene wiring structure 10 usinga liquid crystal according to the first embodiment will be describedspecifically with reference to of the schematic cross-sectional diagramsof FIGS. 8 and 9. These manufacturing methods describe a step for makinga crystal orientation of a graphene between FIGS. 4 and 5 uniform. Thesteps of FIGS. 6 and 7 are common to the above-described manufacturingmethod.

A method for manufacturing the graphene wiring structure 10 includingthe steps of the schematic diagrams illustrated in FIGS. 8 and 9includes a step of providing the microcrystalline graphene 3 on theinsulating film 1, applying a liquid crystal 5 onto the insulating film1 on a side where the microcrystalline graphene 3 is provided and ontothe microcrystalline graphene 3, a step of forming a photo-orientationfilm 6 on the liquid crystal 5, a step of irradiating thephoto-orientation film 6 with polarized light, a step of removing theliquid crystal 5 and the photo-orientation film 6, a step of growing themicrocrystalline graphene 3 into the polycrystalline graphene film 4,and a step of patterning the polycrystalline graphene film 4 into awiring shape.

In the schematic diagram of FIG. 8, the microcrystalline graphene 3 andthe liquid crystal 5 are illustrated on the insulating film 1. Thecrystal orientation of the microcrystalline graphene 3 is random and isprovided on a part of the insulating film 1. The liquid crystal 5 isdisposed in a layered shape so as to cover the insulating film 1 and themicrocrystalline graphene 3. The microcrystalline graphene 3 is disposedbetween the insulating film 1 and the liquid crystal 5.

The member illustrated in the schematic diagram of FIG. 8 ismanufactured by the following method. The multilayered microcrystallinegraphene 3 manufactured by CVD or the like is provided on the insulatingfilm 1. At this time, the insulating film 1 is not a single crystalfilm, and therefore the crystal orientation of the microcrystallinegraphene 3 disposed on the insulating film 1 is random. The liquidcrystal (liquid crystal composition) 5 is applied onto the surface ofthe insulating film 1 on which the randomly oriented microcrystallinegraphene 3 is provided to obtain the member illustrated in the schematicdiagram of FIG. 8.

If an interaction between the liquid crystal 5 and the microcrystallinegraphene 3 is small, it is difficult to control the crystal orientationof the microcrystalline graphene 3 due to the liquid crystal. Therefore,the liquid crystal is preferably a compound having a 6-membered ringstructure in a molecule of the liquid crystal in order to increase theinteraction with the graphene. Suitable examples of the liquid crystalinclude a compound having an azobenzene skeleton and a compound having abiphenyl skeleton.

The photo-orientation film 6 is provided in the member illustrated inthe schematic diagram of FIG. 8 to obtain the member illustrated in theschematic cross-sectional diagram of FIG. 9. The photo-orientation film6 is provided on the liquid crystal 5. Then, the photo-orientation film6 is irradiated with polarized light, and the crystal orientation of themicrocrystalline graphene 3 is controlled together with the liquidcrystal 5. In consideration of a wiring direction, a polarizationdirection for irradiation is selected such that the wiring lengthdirection is the zigzag direction of the graphene. Then, the liquidcrystal 5 and the photo-orientation film 6 are removed to obtain amember having a uniform crystalline orientation of the microcrystallinegraphene 3 as illustrated in FIG. 6. Subsequently, a treatment ofadditional growth of the graphene and patterning into a wiring shape areperformed to obtain the graphene wiring structure 10.

Second Embodiment

A second embodiment is a modified example of the method formanufacturing the graphene wiring structure 10 according to the firstembodiment. The method for manufacturing the graphene wiring structure10 according to the second embodiment includes a step of providing firstmicrocrystalline graphene 3A having a uniform crystal orientation on aninsulating film 1, a step of growing the first microcrystalline graphene3A having a uniform crystal orientation on the insulating film 1 into afirst polycrystalline graphene film 4A, a step of providing secondmicrocrystalline graphene 3B on the first polycrystalline graphene film4A, a step of heating the second microcrystalline graphene 3B on thefirst polycrystalline graphene film 4A to 2000° C. or higher and 3000°C. or lower, a step of growing the heated second microcrystallinegraphene 3B into a second polycrystalline graphene film 4B andlaminating the first polycrystalline graphene film 4A and the secondpolycrystalline graphene film 4B, and a step of patterning the laminatedfirst polycrystalline graphene film 4A and the second polycrystallinegraphene film 4B into a wiring shape.

The second embodiment will be described with reference to the processdiagrams of FIGS. 10A to 10D. FIG. 10A illustrates a member in which thefirst microcrystalline graphene 3A is provided on the insulating film 1.The crystal orientation of this first microcrystalline graphene 3A ismade uniform by the method described in the first embodiment. For themember illustrated in the process diagram of FIG. 10A, additional growthof a graphene is performed in a similar manner to the first embodiment,and the member in which the first polycrystalline graphene film 4A isprovided on the insulating film 1 illustrated in the process diagram ofFIG. 10B is obtained.

Then, as illustrated in the process diagram of FIG. 100, the secondmicrocrystalline graphene 3B is further provided on the firstpolycrystalline graphene film 4A. The crystal orientation of the firstpolycrystalline graphene film 4A is uniform. Therefore, due to aninfluence of crystallinity of the first polycrystalline graphene film4A, the crystal orientation of the second microcrystalline graphene 3Bmay be partly aligned with that of the first polycrystalline graphenefilm 4A. However, not all the orientations of the secondmicrocrystalline graphene 3B are aligned with the orientation of thefirst polycrystalline graphene film 4A. Therefore, if additional growthof a graphene is performed as it is, resistance of the multilayergraphene 2 on an upper layer side is increased. Therefore, in theembodiment, a heat treatment is performed, and the crystal orientationof the second microcrystalline graphene 3B is aligned with the crystalorientation of the first polycrystalline graphene film 4A. In the heattreatment, a region where the second microcrystalline graphene 3B ispresent is preferably subjected to local laser heating. The heatingtemperature is preferably 2000° C. or higher and 3000° C. or lower.Then, as illustrated in the process diagram of FIG. 10D, the secondmicrocrystalline graphene 3B is additionally grown to form the secondpolycrystalline graphene film 4B. A member in which the firstpolycrystalline graphene film 4A and the second polycrystalline graphenefilm 4B are laminated is obtained on the insulating film 1. Thelaminated first polycrystalline graphene film 4A and secondpolycrystalline graphene film 4B are patterned in a wiring shape toobtain the graphene wiring structure 10. Also in FIGS. 10A to 10D, grainboundaries of the polycrystalline graphene film 4 is indicated by abroken line.

Third Embodiment

A third embodiment is a modified example of the method for manufacturingthe graphene wiring structure 10 according to the first or secondembodiment. The third embodiment will be described with reference to theprocess diagrams of FIGS. 11A and 11B. FIG. 11A illustrates a member inwhich microcrystalline graphene 3 is provided on an insulating film 1.The crystal orientation of this microcrystalline graphene 3 is madeuniform by the method described in the first embodiment. The laminationnumber of graphenes of this microcrystalline graphene 3 is different.For the member illustrated in the process diagram of FIG. 11A,additional growth of a graphene is performed in a similar manner to thefirst embodiment, and the member in which a polycrystalline graphenefilm 4 is provided on the insulating film 1 illustrated in the processdiagram of FIG. 11B is obtained. The lamination number of graphenes ofthe microcrystalline graphene 3 is different at the stage illustrated inthe process diagram of FIG. 11A. Therefore, a grain boundary is notpresent on an upper layer side of the polycrystalline graphene film 4,but a grain boundary is present on a lower layer side thereof in FIG.11B. Even with the polycrystalline graphene film 4, by making thecrystal orientation of the microcrystalline graphene 3 uniform, thegraphene wiring structure 10 obtained by patterning the polycrystallinegraphene film 4 into a wiring shape has low resistance. Also in FIGS.11A and 11B, a grain boundary of the polycrystalline graphene film 4 isindicated by a broken line.

Fourth Embodiment

A fourth embodiment is a modified example of the graphene wiringstructure 10 according to the first embodiment. FIG. 12 illustrates aschematic cross-sectional diagram of a graphene wiring structure 20according to the fourth embodiment. The wiring structure 20 according tothe fourth embodiment includes an insulating film 21 and a wiring layer22 having a uniform crystal orientation on the insulating film 21.Crystals of the wiring layer 22 preferably have the zigzag directionoriented at 17 degrees or less with respect to the electric conductiondirection.

A method for manufacturing the wiring structure 20 according to thefourth embodiment includes a step of providing a crystal layer 23 on theinsulating film 21, a step of applying a liquid crystal 24, a monomer25, and a polymerization initiator 26 onto the crystal layer 23, a stepof irradiating the liquid crystal 24, the monomer 25, and thepolymerization initiator 26 on the crystal layer 23 with a polarizedultraviolet ray, and polymerizing the monomer 25 on a crystal layer 23Ain which crystals are oriented in a polarization direction to form apolymer mask 27 on the crystal layer 23A, a step of removing the liquidcrystal 24, the monomer 25, and the polymerization initiator 26 on acrystal layer 23B in which crystals are not oriented in an ultravioletray polarization direction, and the liquid crystal 24 and thepolymerization initiator 26 on the crystal layer 23A in which crystalsare oriented in the polarization direction, a step of etching thecrystal layer 23B in which crystals are not oriented in the ultravioletray polarization direction using the polymer mask 27, a step of removingthe polymer mask 27 on the crystal layer 23A in which crystals have beenoriented in the ultraviolet ray polarization direction, a step ofadditionally growing the crystal layer 23A in which crystals have beenoriented in the ultraviolet ray polarization direction into a crystalfilm 28, and a step of patterning the crystal film 28 into a wiringshape.

The insulating film 21 is the insulating film 1 according to the firstembodiment and is an amorphous or polycrystalline film.

The wiring layer 22 is a conductive member having uniform crystalorientation. The wiring layer 22 is the multilayer graphene 2 accordingto the first embodiment or hexagonal boron nitride. Like the multilayergraphene 2, crystals of hexagonal boron nitride preferably has thezigzag direction oriented at 17 degrees or less with respect to theelectric conduction direction.

Next, a method for manufacturing the wiring structure 20 according tothe fourth embodiment will be described with reference to the drawings.The process diagrams of the wiring structure 20 illustrated in FIGS. 13to 19 are process diagrams for manufacturing the wiring structure 20illustrated in the schematic diagram of FIG. 12. FIGS. 13 to 19 are topdiagrams viewed from a Y direction.

First, as illustrated in the process diagram of FIG. 13, a plurality ofthe crystal layers 23 is provided on the insulating film 21. The crystalorientation of the plurality of crystal layers 23 is not uniform, andtherefore is random. The crystal layer 23 is preferably multilayergraphene, multilayer hexagonal boron nitride, or the like.

Subsequently, as illustrated in the process diagram of FIG. 14, theliquid crystal 24, the monomer 25, and the polymerization initiator 26are applied onto the crystal layer 23. The liquid crystal 24 and thepolymerization initiator 26 are oriented in a direction aligned with thecrystal orientation of the crystal layer 23. The liquid crystal 24, themonomer 25, and the polymerization initiator 26 may also be applied ontothe insulating film 21. The liquid crystal 24 is preferably a compoundhaving a large interaction with a six-membered ring structure containedin the crystal layer 23. Preferred specific examples of the liquidcrystal 24 include a compound having a biphenyl skeleton such as4-cyano-4′-pentylbiphenil. Preferred examples of the monomer 25 includean acrylic monomer such as 2-ethylhexyl acrylate,1,3,3-trimethylhexylacrylate, or n-hexylacrylate. Preferred examples ofthe polymerization initiator 26 include those having a property ofreleasing many radicals when directions of an electric field ofpolarized light and the polymerization initiator are matched like acompound represented by the following chemical formula 1.

For the liquid crystal 24, the monomer 25, and the polymerizationinitiator 26, three kinds of compounds may be used. Alternatively, aliquid crystal monomer and a polymerization initiator, a monomer havinga liquid crystal property and a property as a polymerization initiator,or the like may be used as long as the compound to be applied has thoseproperties.

Subsequently, as illustrated in the process diagram of FIG. 15, theliquid crystal 24, the monomer 25, and the polymerization initiator 26on the crystal layer 23 are irradiated with a polarized ultraviolet ray.By irradiation with a polarized ultraviolet ray, many radicals arereleased from the polymerization initiator 26 oriented in an ultravioletray polarization direction, a polymerization reaction is started, andthe monomer 25 is polymerized to form the polymer mask 27. Thepolymerization reaction proceeds in the crystal layer 23A having acrystal orientation in the same direction as the polarization directionof ultraviolet light, and the polymerization reaction does not proceedin the crystal layer 23B having no crystal orientation in the samedirection as the polarization direction of ultraviolet light. Thepolymer mask 27 is formed on the crystal layer 23A having a crystalorientation in the same direction as the polarization direction ofultraviolet light, and the polymer mask 27 is not formed on the crystallayer 23B having no crystal orientation in the same direction as thepolarization direction of ultraviolet ray.

Subsequently, as illustrated in the process diagram of FIG. 16, theliquid crystal 24, the monomer 25, and the polymerization initiator 26on the crystal layer 23B in which crystals are not oriented in theultraviolet ray polarization direction, and the liquid crystal 24 andthe polymerization initiator 26 on the crystal layer 23A having acrystal orientation in the same direction as the ultraviolet raypolarization direction are removed. As a removal method, it is onlyrequired to perform development using an organic solvent for dissolvingthe liquid crystal 24, the monomer 25, and the polymerization initiator26 but not dissolving the polymer mask 27.

Subsequently, as illustrated in the process diagram of FIG. 17, thecrystal layer 23B in which crystals are not oriented in the ultravioletorientation direction is etched using the polymer mask 27. Removal canbe performed by etching the crystal layer 23B using a reactive ionetching apparatus (RIE) and using O₂ as an etching gas.

Subsequently, as illustrated in the process diagram of FIG. 18, thepolymer mask 27 on the crystal layer 23A in which crystals have beenoriented in the ultraviolet ray polarization direction is removed. It isonly required to anneal the polymer mask 27, for example. By performingannealing or the like, as illustrated in the process diagram of FIG. 18,when the polymer mask 27 is removed, a member in which the crystal layer23A having a uniform crystal orientation is disposed is obtained on theinsulating film 21. The member illustrated in the process diagram ofFIG. 18 has a uniform crystal orientation like the member illustrated inFIG. 5.

Subsequently, as illustrated in the process diagram of FIG. 19, thecrystal layer 23A in which crystals have been oriented in theultraviolet ray polarization direction is additionally grown into thecrystal film 28. A grain boundary of the crystal film 28 is indicated bya broken line. Then, by patterning the crystal film 28 into a wiringshape, the wiring structure of FIG. 12 is obtained. A perspectivediagram of the wiring structure of FIG. 12 is as illustrated in theschematic diagram of FIG. 7.

Incidentally, when the crystal film 28 is grown, crystal orientation maybe deviated, and the crystal film 28 with less deviation in the crystalorientation can be obtained by repeating the steps illustrated in theprocess diagrams of FIGS. 14 to 19. In the process diagrams of FIGS. 13to 19, the crystal layer 23 formed of small crystals is provided on theinsulating film 21, but the present disclosure is not limited thereto.For example, as a modification of the present manufacturing method, byperforming the steps illustrated in the process diagrams of FIGS. 14 to19 on a member in which a polycrystalline crystal layer havingnon-uniform crystal orientation has been formed on the entire surface ofan insulating film 1, portions other than a crystal layer in whichcrystals are oriented in a specific direction (electric conductiondirection of wiring obtained later) are removed. Then, the remainingcrystal layer is additionally grown, and a crystal film having a uniformcrystal orientation can be formed. When the crystal layer 23 alignedwith the ultraviolet ray polarization direction is not present, byrepeating the treatment for providing the crystal layer 23, the wiringstructure 20 according to the fourth embodiment can be obtained.

Fifth Embodiment

A fifth embodiment is a modified example of the graphene wiringstructure 10 of the first embodiment. FIG. 20 illustrates a schematiccross-sectional diagram of the graphene wiring structure according tothe fourth embodiment. A graphene wiring structure 30 of FIG. 20includes a multilayer graphene 2 on an insulating film 1 and aconductive portion 31 electrically connected to the multilayer graphene2 in an insulating film 1. In the fifth embodiment, the wiring structureaccording to the fourth embodiment can also be adopted.

The conductive portion 31 is made of a conductive material including anyone of a metal material including metals such as Cu, Au, Al, W, and Ag,a carbon material such as carbon nanotubes, and the like provided in theinsulating film. When the conductive portion 31 is made of carbonnanotubes, a length direction of the carbon nanotubes is preferably alamination direction of the multilayer graphene 2. The conductiveportion 31 is directly or indirectly in contact with the multilayergraphene 2. The conductive portion 31 is electrically connected to themultilayer graphene 2. The conductive portion 31 constitutes so-calledvia wiring. In the graphene wiring structure 30, a plurality of theconductive portions 31 may be present. The plurality of conductiveportions 31 is electrically connected to each other via the multilayergraphene 2. The conductive portions 31 are, for example, electricallyconnected to a semiconductor element (not illustrated).

In the fifth embodiment, a form in which an element is connected to theconductive portions 31 in the insulating film 1, that is, a form inwhich the multilayer graphene 2 on the insulating film 1 can beconnected to an element under the insulating film 1 is illustrated.However, the connection form between the graphene wiring structureaccording to the fifth embodiment and other elements and the like is notlimited to those illustrated. For example, it is possible to adopt aform in which a conductive member is provided at an end of themultilayer graphene 2 and the multilayer graphene 2 is electricallyconnected to another element via the member, and the like, and theconnection form is not limited. The graphene wiring structure accordingto the fourth embodiment has a more specific configuration in which thelow resistance multilayer graphene 2 can be connected to an externalelement. The multilayer graphene 2 is low resistance wiring. Therefore,a semiconductor device adopting the graphene wiring structure accordingto the fifth embodiment can reduce power consumption and can speed up asignal output via the graphene wiring structure according to the fifthembodiment.

Sixth Embodiment

A sixth embodiment relates to a semiconductor device using the graphenewiring structure according to the first embodiment. The type of thesemiconductor device is not particularly limited, and the semiconductordevice can be adopted for a semiconductor computing device such as alarge-scale integration (LSI), a NAND type flash memory semiconductorstorage device, a system on chip (SoC) including these devices, or thelike.

FIG. 21 illustrates a schematic cross-sectional diagram of athree-dimensional NAND type flash memory as an example of asemiconductor device (semiconductor storage device) 40 using thegraphene wiring structure according to the first embodiment. Thethree-dimensional NAND type flash memory illustrated in FIG. 21 includesa substrate S, a back gate BG, a control gate CG (word line WL), asource side selection gate SGS (selection gate SG), a drain sideselection gate SGD (selection gate SG), a source line SL, a siliconpillar SP, a memory film MM, and a bit line BL. In FIG. 21, six layersof control gates CG are laminated in a lamination direction V, but thepresent disclosure is not limited to this example. In FIG. 21, a memorycell array is disposed on the substrate S.

In the semiconductor device 40 according to the sixth embodiment, thegraphene wiring structure according to the first embodiment is adoptedas the bit line BL. A multilayer graphene of the graphene wiringstructure is electrically connected to the memory film MM. Therefore,the bit line BL becomes low resistance wiring, and contributes to animprovement in signal reading speed. In the sixth embodiment, the wiringstructure according to the fourth embodiment can also be adopted as thebit line BL.

A pillar extending from the bit line BL to the back gate BG is arrangedin a column direction C and a row direction R perpendicular to a crosssection of FIG. 11. The pillar extending from the bit line BL to theback gate BG includes the silicon pillar SP and the memory film MMsurrounding an outside of the silicon pillar SP at the center. Thesilicon pillar SP and the memory film MM are connected to each other inthe back gate BG to form a U shape.

The control gate CG and the selection gate SG extend in the rowdirection R, and a plurality of the control gates CG and the selectiongates SG is arranged in the column direction C. In addition, the bitline BL extends in the column direction C, and a plurality of the bitlines BL is arranged in the row direction R.

The silicon pillar SP, the memory film MM around the silicon pillar SP,and various gates (control gate CG, selection gate SG, and back gate BG)constitute a memory cell transistor MTr as a memory cell, a selectiongate transistor SGTr (drain side selection gate transistor SGDTr, andsource side selection gate transistor SGSTr), and a back gate transistorBTr. The silicon pillar SP functions as a channel and a source/draindiffusion layer of the memory cell transistor MTr, the selection gatetransistor SGTr, and the back gate transistor BTr.

Between the drain side selection gate transistor SGDTr and the sourceside selection gate transistor SGSTr, a plurality of current paths ofthe memory cell transistor MTr and the back gate transistor BTr areconnected in series. A memory string MS is thereby formed.

The source line SL extends in the row direction R while connecting endsof U-shaped memory strings MS adjacent in the column direction C. Thebit line BL extends in the column direction C while connecting thememory strings MS arranged in the column direction C.

A contact is connected to each of ends of the source line SL, the backgate BG, the source side selection gate SGS, and the drain sideselection gate SGD in the row direction R. A contact is connected toeach of stages of a plurality of the word lines WL. Each of thesecontacts is connected to wiring (none of these is illustrated).

In the memory cell array illustrated in FIG. 11, various transistorssuch as the memory cell transistor MTr are three-dimensionally arrangedin a matrix shape. The memory cell array includes an assembly of thesevarious transistors.

In the embodiment, a storage method of the memory cell may be atwo-value storage method, a multi-value storage method, or the like.Data can be written or erased by controlling charge accumulation of aselected memory cell, and data can be read out from judgment of athreshold voltage changing according to the charge accumulation amount.

In the above embodiment, an example in which the memory string MS has aU-shape having a portion where the silicon pillar SP is connected to thememory film MM has been described, but the present disclosure is notlimited thereto. For example, the memory string MS may have an I-shapehaving no connecting portion.

Here, some elements are expressed only by element symbols thereof.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the inventions.

What is claimed is:
 1. A graphene wiring structure comprising: anamorphous or polycrystalline insulating film; and a multilayer grapheneon the amorphous or polycrystalline insulating film, the multilayergraphene including a plurality of graphene crystals having a zigzagdirection oriented at 17 degrees or less with respect to an electricconduction direction, wherein the zigzag direction of the plurality ofgraphene crystals which are oriented linearly is uniform within 17degrees with respect to the electric conduction direction.
 2. Thestructure according to claim 1, wherein the multilayer graphene is alaminate of a plurality of strip-shaped graphene sheets.
 3. Thestructure according to claim 1, further comprising a cyclic structure ofa five-membered ring or a seven-membered ring in the graphene crystals.4. The structure according to claim 1, wherein the average particlediameter of the plurality of graphene crystals is larger than the widthof the multilayer graphene.
 5. The structure according to claim 1,wherein the electric conduction direction is a longitudinal direction ofthe multilayer graphene.
 6. The structure according to claim 1, whereinthe zigzag direction of the plurality of graphene crystals with respectto the electric conduction direction is 1 degree or more.
 7. Thestructure according to claim 1, wherein the amorphous or polycrystallineinsulating film contains at least one selected from the group consistingof SiO₂, Al₂O₃, and TiO₂.
 8. The structure according to claim 1, furthercomprising a conductive portion electrically connected to the multilayergraphene in the amorphous or polycrystalline insulating film.
 9. Thestructure according to claim 1, wherein the plurality of graphenecrystals has the zigzag direction oriented at 1 degree or more and 17degrees or less with respect to the electric conduction direction. 10.The structure according to claim 1, wherein the plurality of graphenecrystals has the zigzag direction oriented at 1 degree or more and 13degrees or less with respect to the electric conduction direction. 11.The structure according to claim 1, wherein the plurality of graphenecrystals has the zigzag direction oriented at 1 degree or more and 11degrees or less with respect to the electric conduction direction.
 12. Asemiconductor device using the graphene wiring structure according toclaim
 1. 13. The structure according to claim 1, wherein an entirely ofthe plurality of graphene crystals have the zigzag direction oriented at17 degrees or less with respect to the electric conduction direction.14. A graphene wiring structure comprising: an amorphous orpolycrystalline insulating film; and a multilayer graphene on theamorphous or polycrystalline insulating film, the multilayer grapheneincluding a plurality of graphene crystals, wherein an entirely of theplurality of graphene crystals have a zigzag direction oriented at 17degrees or less with respect to the electric conduction direction. 15.The structure according to claim 14, wherein the plurality of graphenecrystals has the zigzag direction oriented at 1 degree or more and 17degrees or less with respect to the electric conduction direction. 16.The structure according to claim 14, wherein the plurality of graphenecrystals has the zigzag direction oriented at 1 degree or more and 13degrees or less with respect to the electric conduction direction. 17.The structure according to claim 1, wherein a crystallinity of theplurality of the graphene crystals is not corresponding to acrystallinity of the amorphous or polycrystalline insulating film. 18.The structure according to claim 14, a crystallinity of the plurality ofthe graphene crystals is not corresponding to a crystallinity of theamorphous or polycrystalline insulating film.
 19. The structureaccording to claim 1, the multilayer graphene is directly on theamorphous or polycrystalline insulating film.
 20. The structureaccording to claim 14, the multilayer graphene is directly on theamorphous or polycrystalline insulating film.